Sometimes the simplest things can brighten your rainy commute to work. To wit: as I was making my way to the Guardian's offices this morning, I noticed that each of the small trees growing along York Way had been adorned with a small laminated public notice, presumably put there by Islington council. It said:

"In this time of drought, there is a real risk that some of our trees will suffer greatly if they do not receive enough water. When water is scarce, residents can water Islington's trees using water that usually goes to waste. Grey water from washing up, bathing, car washing and rain water are all appropriate. The soap content (No bleach please!) does not matter to the tree and this way incurs zero cost to you for helping the tree. Healthy trees are essential in the water cycle."

A 'guerrilla gardener' plants a flower under a statue in London Photograph: Andrew Stuart

Never mind that I stood reading it in the rain (the official drought status has been lifted in most of the country), the message still made me smile. Are there many dedicated souls who would haul buckets of dirty bathwater back and forth from their house to make sure trees would make it through the spring? Would many dedicated gardeners be ready to sacrifice their precious rainwater for the sake of beautifying public streets, rather than their own backyards? Possibly. Or at least I'd like to believe so.

Watering street trees isn't exactly guerrilla gardening (of which my favourite is seed bombing, requiring plants enthusiasts to throw seed balls into often privately owned land to embellish neighbourhoods). Nor is it as time-consuming as volunteering to clean up your local park (my neighbourhood organises well-attended cleaning up and seed swapping events) or take responsibility of an entire flowerbed (a good gardening samaritan took charge of the beds in front of my house last year, and courgettes, tomatoes, broccoli and sunflowers were bursting out of them in late summer. What joy).

It is nonetheless a lovely thing to do, and I must tip my hat to those who take it to wonderful extremes: take, for example, the Canadian gardener behind the You Grow Girl blog, who over a decade, built a garden on the side of a building in city-owned land on a very busy public corner, where she had to fight ongoing gentrification, drunk passersby using her garden to relieve themselves, smokers throwing cigarette butts in the cultivated patch and even plant thieves. Call me overly enthusiastic, but people like her are true community heroes.

Is this a gardening philosophy you could ascribe to? Would you water those trees? Have you ever planted flowers in a public space, or done something to embellish your streets and local parks?